What's behind Hawaii's twin storms: Mostly luck

WASHINGTON (AP) -- All sorts of weather factors came together for Hawaii's twin hurricane threat: stuck currents, an oddball brewing El Nino, slightly warmer water but mostly just bad luck.

It's been nearly 22 years without a hurricane hitting Hawaii, and only three direct landfalls since 1950. Hurricane Iselle was aiming dead-on for the Big Island of the 50th state with another hurricane, Julio, right behind. Julio was more likely to be a glancing blow to Hawaii's northern islands, hurricane experts said.

"You roll the dice enough times you get something like this," said Jeff Masters, a former hurricane hunter scientist who is now meteorology director of the private Weather Underground.

The good news is that the hurricanes are coming from the east where storms are weaker and the water cooler, said former National Hurricane Center Director Max Mayfield. Storms coming from the warmer south are more damaging, he said.

But two in a row isn't that weird, Mayfield said: "The steering currents haven't changed and the Central Pacific is active this year."

When conditions are ripe for a hurricane to brew, sometimes another forms in the same area a few days later. The second storm is often guided on the same path as the first, Mayfield and Masters said. It's happened in Florida and North Carolina before.

Julio is the 10th named storm for the eastern Pacific basin, where both storms were born. That usually doesn't happen until early September, Mayfield said. But the eastern Pacific was forecast to be busy this year. The Atlantic and eastern Pacific storm basins are generally mirror images; this year is forecast to be quiet in the Atlantic.

One major factor this year: a sluggish El Nino. The weather event that starts with a warming of the central Pacific has been long forecast. But while some water has warmed, the El Nino hasn't quite formed as expected. The Pacific has more storms during an El Nino and the Atlantic has less. Masters said an almost El Nino probably has some effect but maybe not as much as a full one.

During an El Nino in 1992, the Pacific used all storm names down to Z for Zeke, with Iniki causing $3.1 billion in damage when it hit Hawaii. But it was mostly quiet in the Atlantic. However, one Atlantic storm was more than enough: the devastating Hurricane Andrew, Mayfield said.

Mayfield said global warming isn't a factor at all here.

But in 2013, researchers at the University of Hawaii used computer models to show that as the world warms, steering currents will change and Hawaii will get more hurricanes and Mexico less, Masters said.